'simplify' expression not efficient in Matlab2015

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Kiran Sagar 2016-2-21

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https://ww2.mathworks.cn/matlabcentral/answers/269236-simplify-expression-not-efficient-in-matlab2015

评论： Star Strider 2016-2-21

I used Matlab 2015 to simplify an trigonometric expression, but in vain. It is not able to replace 1-sin^2() with cos^2(). If my memory serves correctly, Matlab2014 was able to do this very efficiently.

Is there a new function that does this in 2015, or we just lost a great feature.

Edit: Inserted Picture

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回答（1 个）

Walter Roberson 2016-2-21

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https://ww2.mathworks.cn/matlabcentral/answers/269236-simplify-expression-not-efficient-in-matlab2015#answer_210667

在 MATLAB Online 中打开

syms theta
simplify( 1 - sin(theta)^2 )

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Kiran Sagar 2016-2-21

编辑：Kiran Sagar 2016-2-21

If I do that, I get the following:

Star Strider 2016-2-21

在 MATLAB Online 中打开

In R2015b:

syms theta
q1 = simplify(1 - sin(theta)^2, 'steps', 10)
q2 = rewrite(1 - sin(theta)^2, 'cos')
q1 =
cos(theta)^2
q2 =
cos(theta)^2

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